Human Body Composition and Fluids

• The objectives are to distinguish body fluid compartments, define normal water values, illustrate physiological variation in total body water, describe the importance of body water, define normal electrolyte values, describe electrolyte importance, and distinguish solution types.
• Human body organization includes cells, tissues, organs, and systems.
• Human body systems include skeletal, muscular, circulatory, digestive, urinary, nervous, reproductive, lymphatic, endocrine, and respiratory systems.

Composition of the Human body

• Water comprises 60% of body weight (BW).
• Other components make up 40% of BW.
• Proteins make up to 18% of BW
• Fats make up 15% of BW.
• Electrolytes make up 7% of BW.

Body Fluid Compartments

• A normal adult young male weighing 70kg contains 60% water distributed across two major compartments.
• The brain and kidneys contain 83% water.
• Lungs contain 85% water
• Eyes contain 95% water
• Heart and muscles contain 75% water
• Blood contains 94% water

Total Body Water

• ICF: intracellular fluid is 2/3 of TBW
• ECF: extracellular fluid is 1/3 of TBW
• ISF: Interstitial fluid is 25% of TBW
• Plasma is 8% of TBW
• Plasma is 1/4 of ECF
• Interstitial fluid is 3/4 of ECF
• Intracellular fluid is 2/3 of TBW
• Total Body Water (TBW) is 60% of body weight

Factors Affecting TBW

• Physiological factors include age, sex, and body fat.
• Pathological factors include vomiting, diarrhea, diseases with excessive water loss (DM, excessive sweating), blood loss, and burns.
• Other factors include climate, habits, and physical activity.
• Disturbances in TBW cause disturbances in fluid balance.
• Low body fat and low bone mass means 73% or more water in babies.
• Higher body fat and a smaller amount of skeletal muscles mean 40-50% water.
• 60% of body weight is water in middle aged people.
• Only about 45% of body weight is water for elderly people.

Importance of Body Water

• Water constitutes no less than 40% of TBW in any living organism.
• Water acts as a solvent for digestion, absorption, secretion, exertion, and mobility of ions.
• Water has ionizing properties and dissociates into OH- and H+ ions.

Other Benefits of Body Water

• Water is essential for all sensations except the tactile sense.
• Water supports body temperature regulation
• Water makes tissue pliable and flexible.

Body Electrolytes

– The normal electrolyte value accounts for 7% of body fluids.

• Electrolytes maintain osmolarity of body fluids, measured in osmoles/kg of solvent.
• Each electrolyte has a specific function (e.g., Ca++ in bone mineralization).
• Electrolytes determine cell membrane potential and water content and distribution.
• Electrolytes are affected by acid-base balance.

Types of Solutions

• True solutions have a particle size of less than 1mm, are stable and homogenous, and pass freely through semi-permeable filters (e.g., NaCl–glucose solution).
• Colloidal solutions have a particle size of 1-200 mm, are stable and homogenous, and cannot pass through filters (e.g., egg albumin and starch solution).
• Suspension solutions have a particle size greater than 200mm, are unstable and precipitate, and cannot pass through filters (e.g., blood, sand, and charcoal solution).

Definitions

• Cells are the smallest independent microscopic structural unit.
• Tissue consists of cells with similar structure and function.
• Organs consist of different types of tissues that perform specific functions.
• Systems consist of a group of organs that perform specific functions.

Understand body fluid compartments, normal water values, and physiological variations in total body water. Learn about the importance of body water and normal electrolyte values. Explore the composition of the human body, including water, proteins, fats, and electrolytes, and how they're distributed.